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HTTP/1.1, part 2: Message SemanticsAdobe Systems Incorporated345 Park AveSan JoseCA95110USAfielding@gbiv.comhttp://roy.gbiv.com/Alcatel-Lucent Bell Labs21 Oak Knoll RoadCarlisleMA01741USAjg@freedesktop.orghttp://gettys.wordpress.com/Hewlett-Packard CompanyHP Labs, Large Scale Systems Group1501 Page Mill Road, MS 1177Palo AltoCA94304USAJeffMogul@acm.orgMicrosoft Corporation1 Microsoft WayRedmondWA98052USAhenrikn@microsoft.comAdobe Systems Incorporated345 Park AveSan JoseCA95110USALMM@acm.orghttp://larry.masinter.net/Microsoft Corporation1 Microsoft WayRedmondWA98052paulle@microsoft.comWorld Wide Web ConsortiumMIT Computer Science and Artificial Intelligence LaboratoryThe Stata Center, Building 3232 Vassar StreetCambridgeMA02139USAtimbl@w3.orghttp://www.w3.org/People/Berners-Lee/World Wide Web ConsortiumW3C / ERCIM2004, rte des LuciolesSophia-AntipolisAM06902Franceylafon@w3.orghttp://www.raubacapeu.net/people/yves/greenbytes GmbHHafenweg 16MuensterNW48155Germany+49 251 2807760+49 251 2807761julian.reschke@greenbytes.dehttp://greenbytes.de/tech/webdav/HTTPbis Working Group
The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
distributed, collaborative, hypertext information systems. HTTP has been in
use by the World Wide Web global information initiative since 1990. This
document is Part 2 of the seven-part specification that defines the protocol
referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
Part 2 defines the semantics of HTTP messages as expressed by request
methods, request header fields, response status codes, and response header
fields.
Discussion of this draft should take place on the HTTPBIS working group
mailing list (ietf-http-wg@w3.org), which is archived at
.
The current issues list is at
and related
documents (including fancy diffs) can be found at
.
The changes in this draft are summarized in .
This document defines HTTP/1.1 request and response semantics. Each HTTP
message, as defined in &messaging;, is in the form of either a request or
a response. An HTTP server listens on a connection for HTTP requests and
responds to each request, in the order received on that connection, with
one or more HTTP response messages. This document defines the commonly
agreed upon semantics of the HTTP uniform interface, the intentions defined
by each request method, and the various response messages that might be
expected as a result of applying that method to the target resource.
This document is currently disorganized in order to minimize the changes
between drafts and enable reviewers to see the smaller errata changes.
A future draft will reorganize the sections to better reflect the content.
In particular, the sections will be ordered according to the typical
processing of an HTTP request message (after message parsing): resource
mapping, methods, request modifying header fields, response status,
status modifying header fields, and resource metadata. The current mess
reflects how widely dispersed these topics and associated requirements
had become in .
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in .
This document defines conformance criteria for several roles in HTTP
communication, including Senders, Recipients, Clients, Servers, User-Agents,
Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
for definitions of these terms.
An implementation is considered conformant if it complies with all of the
requirements associated with its role(s). Note that SHOULD-level requirements
are relevant here, unless one of the documented exceptions is applicable.
This document also uses ABNF to define valid protocol elements
(). In addition to the prose requirements placed
upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
Unless noted otherwise, Recipients &MAY; take steps to recover a usable
protocol element from an invalid construct. However, HTTP does not define
specific error handling mechanisms, except in cases where it has direct
impact on security. This is because different uses of the protocol require
different error handling strategies; for example, a Web browser may wish to
transparently recover from a response where the Location header field
doesn't parse according to the ABNF, whereby in a systems control protocol
using HTTP, this type of error recovery could lead to dangerous consequences.
This specification uses the ABNF syntax defined in &notation; (which
extends the syntax defined in with a list rule).
shows the collected ABNF, with the list
rule expanded.
The following core rules are included by
reference, as defined in :
ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
DIGIT (decimal 0-9), DQUOTE (double quote),
HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
OCTET (any 8-bit sequence of data), SP (space), and
VCHAR (any visible US-ASCII character).
The core rules below are defined in :
BWS = <BWS, defined in &basic-rules;>
OWS = <OWS, defined in &basic-rules;>
RWS = <RWS, defined in &basic-rules;>
obs-text = <obs-text, defined in &basic-rules;>
quoted-string = <quoted-string, defined in &field-rules;>
token = <token, defined in &field-rules;>
The ABNF rules below are defined in other parts:
absolute-URI = <absolute-URI, defined in &uri;>
comment = <comment, defined in &header-fields;>
partial-URI = <partial-URI, defined in &uri;>
product = <product, defined in &product-tokens;>
URI-reference = <URI-reference, defined in &uri;>
The Method token indicates the request method to be performed on the target
resource (&effective-request-uri;). The method is case-sensitive.
Method = token
The list of methods allowed by a resource can be specified in an
Allow header field (). The status code of the response
always notifies the client whether a method is currently allowed on a
resource, since the set of allowed methods can change dynamically. An
origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
if the method is known by the origin server but not allowed for the
resource, and 501 (Not Implemented) if the method is
unrecognized or not implemented by the origin server. The methods GET
and HEAD &MUST; be supported by all general-purpose servers. All other
methods are &OPTIONAL;; however, if the above methods are implemented,
they &MUST; be implemented with the same semantics as those specified
in .
The methods listed below are defined in .
Method NameDefined in...OPTIONSGETHEADPOSTPUTDELETETRACECONNECT
Note that this list is not exhaustive — it does not include request methods defined
in other specifications.
The HTTP Method Registry defines the name space for the Method token in the
Request line of an HTTP request.
Registrations &MUST; include the following fields:
Method Name (see )Safe ("yes" or "no", see )Pointer to specification text
Values to be added to this name space are subject to IETF review
().
The registry itself is maintained at .
When it is necessary to express new semantics for a HTTP request that
aren't specific to a single application or media type, and currently defined
methods are inadequate, it may be appropriate to register a new method.
HTTP methods are generic; that is, they are potentially applicable to any
resource, not just one particular media type, "type" of resource, or
application. As such, it is preferred that new HTTP methods be registered
in a document that isn't specific to a single application, so that this is
clear.
Due to the parsing rules defined in &message-body;, definitions of HTTP
methods cannot prohibit the presence of a message-body on either the request
or the response message (with responses to HEAD requests being the single
exception). Definitions of new methods cannot change this rule, but they can
specify that only zero-length bodies (as opposed to absent bodies) are allowed.
New method definitions need to indicate whether they are safe (), what semantics (if any) the request body has,
and whether they are idempotent ().
They also need to state whether they can be cached (&caching;); in
particular what conditions a cache may store the response, and under what
conditions such a stored response may be used to satisfy a subsequent
request.
Header fields are key value pairs that can be used to communicate data about
the message, its payload, the target resource, or about the connection
itself (i.e., control data). See &header-fields; for a general definition
of their syntax.
New header fields are registered using the procedures described in
.
The requirements for header field names are defined in
. Authors of specifications
defining new fields are advised to keep the name as short as practical, and
not to prefix them with "X-" if they are to be registered (either
immediately or in the future).
New header field values typically have their syntax defined using ABNF
(), using the extensions defined in &notation-abnf;
as necessary, and are usually constrained to the range of ASCII characters.
Header fields needing a greater range of characters can use an encoding
such as the one defined in .
Because commas (",") are used as a generic delimiter between field-values,
they need to be treated with care if they are allowed in the field-value's
payload. Typically, components that might contain a comma are protected with
double-quotes using the quoted-string ABNF production (&field-rules;).
For example, a textual date and a URI (either of which might contain a comma)
could be safely carried in field-values like these:
Example-URI-Field: "http://example.com/a.html,foo",
"http://without-a-comma.example.com/"
Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
Note that double quote delimiters almost always are used with the
quoted-string production; using a different syntax inside double quotes
will likely cause unnecessary confusion.
Many header fields use a format including (case-insensitively) named
parameters (for instance, Content-Type, defined in &header-content-type;).
Allowing both unquoted (token) and quoted (quoted-string) syntax for the
parameter value enables recipients to use existing parser components. When
allowing both forms, the meaning of a parameter value ought to be
independent of the syntax used for it (for an example, see the notes on
parameter handling for media types in &media-types;).
Authors of specifications defining new header fields are advised to consider
documenting:
Whether the field is a single value, or whether it can be a list
(delimited by commas; see &header-fields;).If it does not use the list syntax, document how to treat messages
where the header field occurs multiple times (a sensible default would
be to ignore the header field, but this might not always be the right
choice).Note that intermediaries and software libraries might combine
multiple header field instances into a single one, despite the header
field not allowing this. A robust format enables recipients to discover
these situations (good example: "Content-Type", as the comma can only
appear inside quoted strings; bad example: "Location", as a comma can
occur inside a URI).Under what conditions the header field can be used; e.g., only in
responses or requests, in all messages, only on responses to a particular
request method.Whether it is appropriate to list the field-name in the Connection header
(i.e., if the header is to be hop-by-hop, see &header-connection;).Under what conditions intermediaries are allowed to modify the header
field's value, insert or delete it.How the header might interact with caching (see ).Whether the header field is useful or allowable in trailers (see
&chunked-encoding;).Whether the header field should be preserved across redirects.
The request header fields allow the client to pass additional
information about the request, and about the client itself, to the
server. These fields act as request modifiers, with semantics
equivalent to the parameters on a programming language method
invocation.
Header Field NameDefined in...Accept&header-accept;Accept-Charset&header-accept-charset;Accept-Encoding&header-accept-encoding;Accept-Language&header-accept-language;Authorization&header-authorization;ExpectFromHost&header-host;If-Match&header-if-match;If-Modified-Since&header-if-modified-since;If-None-Match&header-if-none-match;If-Range&header-if-range;If-Unmodified-Since&header-if-unmodified-since;Max-ForwardsProxy-Authorization&header-proxy-authorization;Range&header-range;RefererTE&header-te;User-Agent
The response header fields allow the server to pass additional
information about the response which cannot be placed in the Status-Line.
These header fields give information about the server and about
further access to the target resource (&effective-request-uri;).
Header Field NameDefined in...Accept-Ranges&header-accept-ranges;Age&header-age;AllowDateETag&header-etag;LocationProxy-Authenticate&header-proxy-authenticate;Retry-AfterServerVary&header-vary;WWW-Authenticate&header-www-authenticate;
The Status-Code element is a 3-digit integer result code of the attempt to
understand and satisfy the request.
The Reason-Phrase is intended to give a short textual description of the
Status-Code and is intended for a human user. The client does not need
to examine or display the Reason-Phrase.
Status-Code = 3DIGITReason-Phrase = *( HTAB / SP / VCHAR / obs-text )
HTTP status codes are extensible. HTTP applications are not required
to understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications &MUST;
understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an
unrecognized response &MUST-NOT; be cached. For example, if an
unrecognized status code of 431 is received by the client, it can
safely assume that there was something wrong with its request and
treat the response as if it had received a 400 status code. In such
cases, user agents &SHOULD; present to the user the representation enclosed
with the response, since that representation is likely to include human-readable
information which will explain the unusual status.
The status codes listed below are defined in
of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
The reason phrases listed here are only recommendations — they can be
replaced by local equivalents without affecting the protocol.
Status-CodeReason-PhraseDefined in...100Continue101Switching Protocols200OK201Created202Accepted203Non-Authoritative Information204No Content205Reset Content206Partial Content&status-206;300Multiple Choices301Moved Permanently302Found303See Other304Not Modified&status-304;305Use Proxy307Temporary Redirect400Bad Request401Unauthorized&status-401;402Payment Required403Forbidden404Not Found405Method Not Allowed406Not Acceptable407Proxy Authentication Required&status-407;408Request Time-out409Conflict410Gone411Length Required412Precondition Failed&status-412;413Request Representation Too Large414URI Too Long415Unsupported Media Type416Requested range not satisfiable&status-416;417Expectation Failed426Upgrade Required500Internal Server Error501Not Implemented502Bad Gateway503Service Unavailable504Gateway Time-out505HTTP Version not supported
Note that this list is not exhaustive — it does not include
extension status codes defined in other specifications.
The HTTP Status Code Registry defines the name space for the Status-Code
token in the Status-Line of an HTTP response.
Values to be added to this name space are subject to IETF review
().
The registry itself is maintained at .
When it is necessary to express new semantics for a HTTP response that
aren't specific to a single application or media type, and currently defined
status codes are inadequate, a new status code can be registered.
HTTP status codes are generic; that is, they are potentially applicable to
any resource, not just one particular media type, "type" of resource, or
application. As such, it is preferred that new HTTP status codes be
registered in a document that isn't specific to a single application, so
that this is clear.
Definitions of new HTTP status codes typically explain the request
conditions that produce a response containing the status code (e.g.,
combinations of request headers and/or method(s)), along with any
interactions with response headers (e.g., those that are required, those
that modify the semantics of the response).
New HTTP status codes are required to fall under one of the categories
defined in . To allow existing parsers to
properly handle them, new status codes cannot disallow a response body,
although they can mandate a zero-length response body. They can require the
presence of one or more particular HTTP response header(s).
Likewise, their definitions can specify that caches are allowed to use
heuristics to determine their freshness (see &caching;; by default, it is
not allowed), and can define how to determine the resource which they
carry a representation for (see ; by default,
it is anonymous).
Request and Response messages &MAY; transfer a representation if not otherwise
restricted by the request method or response status code. A representation
consists of metadata (representation header fields) and data (representation
body). When a complete or partial representation is enclosed in an HTTP message,
it is referred to as the payload of the message. HTTP representations
are defined in &payload;.
A representation body is only present in a message when a message-body is
present, as described in &message-body;. The representation body is obtained
from the message-body by decoding any Transfer-Encoding that might
have been applied to ensure safe and proper transfer of the message.
It is sometimes necessary to determine an identifier for the resource
associated with a representation.
An HTTP request representation, when present, is always associated with an
anonymous (i.e., unidentified) resource.
In the common case, an HTTP response is a representation of the target
resource (see &effective-request-uri;). However, this is not always the
case. To determine the URI of the resource a response is associated with,
the following rules are used (with the first applicable one being selected):
If the response status code is 200 or 203 and the request method was GET,
the response payload is a representation of the target resource.If the response status code is 204, 206, or 304 and the request method was GET
or HEAD, the response payload is a partial representation of the target
resource.If the response has a Content-Location header field, and that URI is the same
as the effective request URI, the response payload is a representation of the
target resource.If the response has a Content-Location header field, and that URI is not the
same as the effective request URI, then the response asserts that its
payload is a representation of the resource identified by the
Content-Location URI. However, such an assertion cannot be trusted unless
it can be verified by other means (not defined by HTTP).Otherwise, the response is a representation of an anonymous (i.e.,
unidentified) resource.
The comparison function is going to have to be defined somewhere,
because we already need to compare URIs for things like cache invalidation.
The set of common request methods for HTTP/1.1 is defined below. Although
this set can be expanded, additional methods cannot be assumed to
share the same semantics for separately extended clients and servers.
Implementors need to be aware that the software represents the user in
their interactions over the Internet, and need to allow
the user to be aware of any actions they take which might have an
unexpected significance to themselves or others.
In particular, the convention has been established that the GET, HEAD,
OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
of taking an action other than retrieval. These request methods ought
to be considered "safe".
This allows user agents to represent other methods, such as POST, PUT
and DELETE, in a special way, so that the user is made aware of the
fact that a possibly unsafe action is being requested.
Naturally, it is not possible to ensure that the server does not
generate side-effects as a result of performing a GET request; in
fact, some dynamic resources consider that a feature. The important
distinction here is that the user did not request the side-effects,
so therefore cannot be held accountable for them.
Request methods can also have the property of "idempotence" in that,
aside from error or expiration issues, the intended effect of multiple
identical requests is the same as for a single request.
PUT, DELETE, and all safe request methods are idempotent.
It is important to note that idempotence refers only to changes
requested by the client: a server is free to change its state due
to multiple requests for the purpose of tracking those requests,
versioning of results, etc.
yes
The OPTIONS method requests information about the
communication options available on the request/response chain
identified by the effective request URI. This method allows a client to
determine the options and/or requirements associated with a resource,
or the capabilities of a server, without implying a resource action
or initiating a resource retrieval.
Responses to the OPTIONS method are not cacheable.
If the OPTIONS request includes a message-body (as indicated by the
presence of Content-Length or Transfer-Encoding), then the media type
&MUST; be indicated by a Content-Type field. Although this
specification does not define any use for such a body, future
extensions to HTTP might use the OPTIONS body to make more detailed
queries on the server.
If the request-target is an asterisk ("*"), the OPTIONS request is
intended to apply to the server in general rather than to a specific
resource. Since a server's communication options typically depend on
the resource, the "*" request is only useful as a "ping" or "no-op"
type of method; it does nothing beyond allowing the client to test
the capabilities of the server. For example, this can be used to test
a proxy for HTTP/1.1 compliance (or lack thereof).
If the request-target is not an asterisk, the OPTIONS request applies
only to the options that are available when communicating with that
resource.
A 200 response &SHOULD; include any header fields that indicate
optional features implemented by the server and applicable to that
resource (e.g., Allow), possibly including extensions not defined by
this specification. The response body, if any, &SHOULD; also include
information about the communication options. The format for such a
body is not defined by this specification, but might be defined by
future extensions to HTTP. Content negotiation &MAY; be used to select
the appropriate response format. If no response body is included, the
response &MUST; include a Content-Length field with a field-value of
"0".
The Max-Forwards header field &MAY; be used to target a
specific proxy in the request chain (see ).
If no Max-Forwards field is present in the request, then the forwarded
request &MUST-NOT; include a Max-Forwards field.
yes
The GET method requests transfer of a current representation of
the target resource.
If the target resource is a data-producing process, it is the
produced data which shall be returned as the representation in the response and not
the source text of the process, unless that text happens to be the output of
the process.
The semantics of the GET method change to a "conditional GET" if the
request message includes an If-Modified-Since, If-Unmodified-Since,
If-Match, If-None-Match, or If-Range header field. A conditional GET
requests that the representation be transferred only under the
circumstances described by the conditional header field(s). The
conditional GET request is intended to reduce unnecessary network
usage by allowing cached representations to be refreshed without requiring
multiple requests or transferring data already held by the client.
The semantics of the GET method change to a "partial GET" if the
request message includes a Range header field. A partial GET requests
that only part of the representation be transferred, as described in &header-range;.
The partial GET request is intended to reduce unnecessary
network usage by allowing partially-retrieved representations to be
completed without transferring data already held by the client.
Bodies on GET requests have no defined semantics. Note that sending a body
on a GET request might cause some existing implementations to reject the
request.
The response to a GET request is cacheable and &MAY; be used to satisfy
subsequent GET and HEAD requests (see &caching;).
See for security considerations when used for forms.
yes
The HEAD method is identical to GET except that the server &MUST-NOT;
return a message-body in the response. The metadata contained
in the HTTP header fields in response to a HEAD request &SHOULD; be identical
to the information sent in response to a GET request. This method can
be used for obtaining metadata about the representation implied by the
request without transferring the representation body. This method is
often used for testing hypertext links for validity, accessibility,
and recent modification.
The response to a HEAD request is cacheable and &MAY; be used to satisfy
a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
representation from that resource; if the new field values
indicate that the cached representation differs from the current representation (as
would be indicated by a change in Content-Length, ETag
or Last-Modified), then the cache &MUST; treat the cache entry as
stale.
Bodies on HEAD requests have no defined semantics. Note that sending a body
on a HEAD request might cause some existing implementations to reject the
request.
The POST method requests that the origin server accept the
representation enclosed in the request as data to be processed by the
target resource. POST is designed to allow a uniform method to cover the
following functions:
Annotation of existing resources;
Posting a message to a bulletin board, newsgroup, mailing list,
or similar group of articles;
Providing a block of data, such as the result of submitting a
form, to a data-handling process;
Extending a database through an append operation.
The actual function performed by the POST method is determined by the
server and is usually dependent on the effective request URI.
The action performed by the POST method might not result in a
resource that can be identified by a URI. In this case, either 200
(OK) or 204 (No Content) is the appropriate response status code,
depending on whether or not the response includes a representation that
describes the result.
If a resource has been created on the origin server, the response
&SHOULD; be 201 (Created) and contain a representation which describes the
status of the request and refers to the new resource, and a Location
header field (see ).
Responses to POST requests are only cacheable when they
include explicit freshness information (see &p6-explicit;). A
cached POST response with a Content-Location header field
(see &header-content-location;) whose value is the effective
Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
Note that POST caching is not widely implemented.
However, the 303 (See Other) response can be used to direct the
user agent to retrieve a cacheable resource.
The PUT method requests that the state of the target resource
be created or replaced with the state defined by the representation
enclosed in the request message payload. A successful PUT of a given
representation would suggest that a subsequent GET on that same target
resource will result in an equivalent representation being returned in
a 200 (OK) response. However, there is no guarantee that such a state
change will be observable, since the target resource might be acted
upon by other user agents in parallel, or might be subject to dynamic
processing by the origin server, before any subsequent GET is received.
A successful response only implies that the user agent's intent was
achieved at the time of its processing by the origin server.
If the target resource does not have a current representation and
the PUT successfully creates one, then the origin server &MUST; inform
the user agent by sending a 201 (Created) response. If the target
resource does have a current representation and that representation is
successfully modified in accordance with the state of the enclosed
representation, then either a 200 (OK) or 204 (No Content) response
&SHOULD; be sent to indicate successful completion of the request.
Unrecognized header fields &SHOULD; be ignored (i.e., not saved
as part of the resource state).
An origin server &SHOULD; verify that the PUT representation is
consistent with any constraints which the server has for the target
resource that cannot or will not be changed by the PUT. This is
particularly important when the origin server uses internal
configuration information related to the URI in order to set the
values for representation metadata on GET responses. When a PUT
representation is inconsistent with the target resource, the origin
server &SHOULD; either make them consistent, by transforming the
representation or changing the resource configuration, or respond
with an appropriate error message containing sufficient information
to explain why the representation is unsuitable. The 409 (Conflict)
or 415 (Unsupported Media Type) status codes are suggested, with the
latter being specific to constraints on Content-Type values.
For example, if the target resource is configured to always have a
Content-Type of "text/html" and the representation being PUT has a
Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
(a) reconfigure the target resource to reflect the new media type;
(b) transform the PUT representation to a format consistent with that
of the resource before saving it as the new resource state; or,
(c) reject the request with a 415 response indicating that the target
resource is limited to "text/html", perhaps including a link to a
different resource that would be a suitable target for the new
representation.
HTTP does not define exactly how a PUT method affects the state
of an origin server beyond what can be expressed by the intent of
the user agent request and the semantics of the origin server response.
It does not define what a resource might be, in any sense of that
word, beyond the interface provided via HTTP. It does not define
how resource state is "stored", nor how such storage might change
as a result of a change in resource state, nor how the origin server
translates resource state into representations. Generally speaking,
all implementation details behind the resource interface are
intentionally hidden by the server.
The fundamental difference between the POST and PUT methods is
highlighted by the different intent for the target resource.
The target resource in a POST request is intended to handle the
enclosed representation as a data-accepting process, such as for
a gateway to some other protocol or a document that accepts annotations.
In contrast, the target resource in a PUT request is intended to
take the enclosed representation as a new or replacement value.
Hence, the intent of PUT is idempotent and visible to intermediaries,
even though the exact effect is only known by the origin server.
Proper interpretation of a PUT request presumes that the user agent
knows what target resource is desired. A service that is intended
to select a proper URI on behalf of the client, after receiving
a state-changing request, &SHOULD; be implemented using the POST
method rather than PUT. If the origin server will not make the
requested PUT state change to the target resource and instead
wishes to have it applied to a different resource, such as when the
resource has been moved to a different URI, then the origin server
&MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
then make its own decision regarding whether or not to redirect the
request.
A PUT request applied to the target resource &MAY; have side-effects
on other resources. For example, an article might have a URI for
identifying "the current version" (a resource) which is separate
from the URIs identifying each particular version (different
resources that at one point shared the same state as the current version
resource). A successful PUT request on "the current version" URI might
therefore create a new version resource in addition to changing the
state of the target resource, and might also cause links to be added
between the related resources.
An origin server &SHOULD; reject any PUT request that contains a
Content-Range header field, since it might be misinterpreted as
partial content (or might be partial content that is being mistakenly
PUT as a full representation). Partial content updates are
possible by targeting a separately identified resource with state
that overlaps a portion of the larger resource, or by using a
different method that has been specifically defined for partial
updates (for example, the PATCH method defined in
).
Responses to the PUT method are not cacheable. If a PUT request passes
through a cache that has one or more stored responses for the effective
request URI, those stored responses will be invalidated (see
&p6-invalid;).
The DELETE method requests that the origin server delete the target
resource. This method &MAY; be overridden by
human intervention (or other means) on the origin server. The client cannot
be guaranteed that the operation has been carried out, even if the
status code returned from the origin server indicates that the action
has been completed successfully. However, the server &SHOULD-NOT;
indicate success unless, at the time the response is given, it
intends to delete the resource or move it to an inaccessible
location.
A successful response &SHOULD; be 200 (OK) if the response includes an
representation describing the status, 202 (Accepted) if the action has not
yet been enacted, or 204 (No Content) if the action has been enacted
but the response does not include a representation.
Bodies on DELETE requests have no defined semantics. Note that sending a body
on a DELETE request might cause some existing implementations to reject the
request.
Responses to the DELETE method are not cacheable. If a DELETE request
passes through a cache that has one or more stored responses for the
effective request URI, those stored responses will be invalidated (see
&p6-invalid;).
yes
The TRACE method requests a remote, application-layer loop-back
of the request message. The final recipient of the request
&SHOULD; reflect the message received back to the client as the
message-body of a 200 (OK) response. The final recipient is either the
origin server or the first proxy to receive a Max-Forwards
value of zero (0) in the request (see ).
A TRACE request &MUST-NOT; include a message-body.
TRACE allows the client to see what is being received at the other
end of the request chain and use that data for testing or diagnostic
information. The value of the Via header field (&header-via;) is of
particular interest, since it acts as a trace of the request chain.
Use of the Max-Forwards header field allows the client to limit the
length of the request chain, which is useful for testing a chain of
proxies forwarding messages in an infinite loop.
If the request is valid, the response &SHOULD; have a Content-Type of
"message/http" (see &media-type-message-http;) and contain a message-body
that encloses a copy of the entire request message.
Responses to the TRACE method are not cacheable.
The CONNECT method requests that the proxy establish a tunnel
to the request-target and then restrict its behavior to blind
forwarding of packets until the connection is closed.
When using CONNECT, the request-target &MUST; use the authority form
(&request-target;); i.e., the request-target consists of only the
host name and port number of the tunnel destination, separated by a colon.
For example,
CONNECT server.example.com:80 HTTP/1.1
Host: server.example.com:80
Other HTTP mechanisms can be used normally with the CONNECT method —
except end-to-end protocol Upgrade requests, since the
tunnel must be established first.
For example, proxy authentication might be used to establish the
authority to create a tunnel:
CONNECT server.example.com:80 HTTP/1.1
Host: server.example.com:80
Proxy-Authorization: basic aGVsbG86d29ybGQ=
Bodies on CONNECT requests have no defined semantics. Note that sending a body
on a CONNECT request might cause some existing implementations to reject the
request.
Like any other pipelined HTTP/1.1 request, data to be tunnel may be
sent immediately after the blank line. The usual caveats also apply:
data may be discarded if the eventual response is negative, and the
connection may be reset with no response if more than one TCP segment
is outstanding.
Any successful (2xx) response to a CONNECT request indicates that the
proxy has established a connection to the requested host and port,
and has switched to tunneling the current connection to that server
connection.
It may be the case that the proxy itself can only reach the requested
origin server through another proxy. In this case, the first proxy
&SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
to the authority. A proxy &MUST-NOT; respond with any 2xx status code
unless it has either a direct or tunnel connection established to the
authority.
An origin server which receives a CONNECT request for itself &MAY;
respond with a 2xx status code to indicate that a connection is
established.
If at any point either one of the peers gets disconnected, any
outstanding data that came from that peer will be passed to the other
one, and after that also the other connection will be terminated by
the proxy. If there is outstanding data to that peer undelivered,
that data will be discarded.
The first digit of the Status-Code defines the class of response. The
last two digits do not have any categorization role. There are 5
values for the first digit:
1xx: Informational - Request received, continuing process
2xx: Success - The action was successfully received,
understood, and accepted
3xx: Redirection - Further action must be taken in order to
complete the request
4xx: Client Error - The request contains bad syntax or cannot
be fulfilled
5xx: Server Error - The server failed to fulfill an apparently
valid request
Each Status-Code is described below, including any metadata required
in the response.
This class of status code indicates a provisional response,
consisting only of the Status-Line and optional header fields, and is
terminated by an empty line. There are no required header fields for this
class of status code. Since HTTP/1.0 did not define any 1xx status
codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
except under experimental conditions.
A client &MUST; be prepared to accept one or more 1xx status responses
prior to a regular response, even if the client does not expect a 100
(Continue) status message. Unexpected 1xx status responses &MAY; be
ignored by a user agent.
Proxies &MUST; forward 1xx responses, unless the connection between the
proxy and its client has been closed, or unless the proxy itself
requested the generation of the 1xx response. (For example, if a
proxy adds a "Expect: 100-continue" field when it forwards a request,
then it need not forward the corresponding 100 (Continue)
response(s).)
The client &SHOULD; continue with its request. This interim response is
used to inform the client that the initial part of the request has
been received and has not yet been rejected by the server. The client
&SHOULD; continue by sending the remainder of the request or, if the
request has already been completed, ignore this response. The server
&MUST; send a final response after the request has been completed. See
&use100; for detailed discussion of the use and handling of this
status code.
The server understands and is willing to comply with the client's
request, via the Upgrade message header field (&header-upgrade;), for a
change in the application protocol being used on this connection. The
server will switch protocols to those defined by the response's
Upgrade header field immediately after the empty line which
terminates the 101 response.
The protocol &SHOULD; be switched only when it is advantageous to do
so. For example, switching to a newer version of HTTP is advantageous
over older versions, and switching to a real-time, synchronous
protocol might be advantageous when delivering resources that use
such features.
This class of status code indicates that the client's request was
successfully received, understood, and accepted.
The request has succeeded. The payload returned with the response
is dependent on the method used in the request, for example:
a representation of the target resource is sent in the response;
the same representation as GET, except without the message-body;
a representation describing or containing the result of the action;
a representation containing the request message as received by the
end server.
Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
freshness for 200 responses.
The request has been fulfilled and has resulted in a new resource being
created. The newly created resource can be referenced by the URI(s)
returned in the payload of the response, with the most specific URI
for the resource given by a Location header field. The response
&SHOULD; include a payload containing a list of resource
characteristics and location(s) from which the user or user agent can
choose the one most appropriate. The payload format is specified by
the media type given in the Content-Type header field. The origin
server &MUST; create the resource before returning the 201 status code.
If the action cannot be carried out immediately, the server &SHOULD;
respond with 202 (Accepted) response instead.
A 201 response &MAY; contain an ETag response header field indicating
the current value of the entity-tag for the representation of the resource
just created (see &header-etag;).
The request has been accepted for processing, but the processing has
not been completed. The request might or might not eventually be
acted upon, as it might be disallowed when processing actually takes
place. There is no facility for re-sending a status code from an
asynchronous operation such as this.
The 202 response is intentionally non-committal. Its purpose is to
allow a server to accept a request for some other process (perhaps a
batch-oriented process that is only run once per day) without
requiring that the user agent's connection to the server persist
until the process is completed. The representation returned with this
response &SHOULD; include an indication of the request's current status
and either a pointer to a status monitor or some estimate of when the
user can expect the request to be fulfilled.
The representation in the response has been transformed or otherwise
modified by a transforming proxy (&intermediaries;). Note that the
behaviour of transforming intermediaries is controlled by the no-transform
Cache-Control directive (&header-cache-control;).
This status code is only appropriate when the response status code would
have been 200 (OK) otherwise. When the status code before transformation
would have been different, the 214 Transformation Applied warn-code
(&header-warning;) is appropriate.
Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
freshness for 203 responses.
The 204 (No Content) status code indicates that the server has
successfully fulfilled the request and that there is no additional
content to return in the response payload body. Metadata in the
response header fields refer to the target resource and its current
representation after the requested action.
For example, if a 204 status code is received in response to a PUT
request and the response contains an ETag header field, then the PUT
was successful and the ETag field-value contains the entity-tag for
the new representation of that target resource.
The 204 response allows a server to indicate that the action has been
successfully applied to the target resource while implying that the
user agent &SHOULD-NOT; traverse away from its current "document view"
(if any). The server assumes that the user agent will provide some
indication of the success to its user, in accord with its own interface,
and apply any new or updated metadata in the response to the active
representation.
For example, a 204 status code is commonly used with document editing
interfaces corresponding to a "save" action, such that the document
being saved remains available to the user for editing. It is also
frequently used with interfaces that expect automated data transfers
to be prevalent, such as within distributed version control systems.
The 204 response &MUST-NOT; include a message-body, and thus is always
terminated by the first empty line after the header fields.
The server has fulfilled the request and the user agent &SHOULD; reset
the document view which caused the request to be sent. This response
is primarily intended to allow input for actions to take place via
user input, followed by a clearing of the form in which the input is
given so that the user can easily initiate another input action.
The message-body included with the response &MUST; be empty. Note that
receivers still need to parse the response according to the algorithm defined
in &message-body;.
Part5
The server has fulfilled the partial GET request for the resource
and the enclosed payload is a partial representation as defined in &status-206;.
Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
freshness for 206 responses.
This class of status code indicates that further action needs to be
taken by the user agent in order to fulfill the request. If the required
action involves a subsequent HTTP request, it &MAY; be carried out by the
user agent without interaction with the user if and only if the method used
in the second request is known to be "safe", as defined in
.
There are several types of redirects:
Redirects of the request to another URI, either temporarily or
permanently. The new URI is specified in the Location header field.
In this specification, the status codes 301 (Moved Permanently),
302 (Found), and 307 (Temporary Redirect) fall under this category.
Redirection to a new location that represents an indirect response to
the request, such as the result of a POST operation to be retrieved
with a subsequent GET request. This is status code 303 (See Other).
Redirection offering a choice of matching resources for use by
agent-driven content negotiation (&agent-driven-negotiation;). This
is status code 300 (Multiple Choices).
Other kinds of redirection, such as to a cached result (status code 304
(Not Modified)).
Note: In HTTP/1.0, only the status codes 301 (Moved Permanently)
and 302 (Found) were defined for the first type of redirect, and the second
type did not exist at all ().
However it turned out that web forms using POST expected redirects to change
the operation for the subsequent request to retrieval (GET). To address this
use case, HTTP/1.1 introduced the second type of redirect with the status
code 303 (See Other) ().
As user agents did not change their behavior to maintain backwards
compatibility, the first revision of HTTP/1.1 added yet another status code,
307 (Temporary Redirect), for which the backwards compatibility problems did
not apply ().
Over 10 years later, most user agents still do method rewriting for
status codes 301 and 302, therefore this specification makes that behavior
compliant in case the original request was POST.
A Location header field on a 3xx response indicates that a client &MAY;
automatically redirect to the URI provided; see .
Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
"infinite" redirection loops).
Note: An earlier version of this specification recommended a
maximum of five redirections ().
Content developers need to be aware that some clients might
implement such a fixed limitation.
The target resource has more than one
representation, each with its own specific location, and agent-driven
negotiation information (&content-negotiation;) is being provided so that
the user (or user agent) can select a preferred representation by
redirecting its request to that location.
Unless it was a HEAD request, the response &SHOULD; include a representation
containing a list of representation metadata and location(s) from
which the user or user agent can choose the one most appropriate. The
data format is specified by the media type given in the Content-Type
header field. Depending upon the format and the capabilities of
the user agent, selection of the most appropriate choice &MAY; be
performed automatically. However, this specification does not define
any standard for such automatic selection.
If the server has a preferred choice of representation, it &SHOULD;
include the specific URI for that representation in the Location
field; user agents &MAY; use the Location field value for automatic
redirection.
Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
freshness for 300 responses.
The target resource has been assigned a new permanent URI and any
future references to this resource &SHOULD; use one of the returned
URIs. Clients with link editing capabilities ought to automatically
re-link references to the effective request URI to one or more of the new
references returned by the server, where possible.
Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
freshness for 301 responses.
The new permanent URI &SHOULD; be given by the Location field in the
response. Unless the request method was HEAD, the representation of the
response &SHOULD; contain a short hypertext note with a hyperlink to
the new URI(s).
If the 301 status code is received in response to a request method
that is known to be "safe", as defined in ,
then the request &MAY; be automatically redirected by the user agent without
confirmation. Otherwise, the user agent &MUST-NOT; automatically redirect the
request unless it can be confirmed by the user, since this might
change the conditions under which the request was issued.
Note: For historic reasons, user agents &MAY; change the
request method from POST to GET for the subsequent request. If this
behavior is undesired, status code 307 (Temporary Redirect) can be used
instead.
The target resource resides temporarily under a different URI.
Since the redirection might be altered on occasion, the client &SHOULD;
continue to use the effective request URI for future requests.
The temporary URI &SHOULD; be given by the Location field in the
response. Unless the request method was HEAD, the representation of the
response &SHOULD; contain a short hypertext note with a hyperlink to
the new URI(s).
If the 302 status code is received in response to a request method
that is known to be "safe", as defined in ,
then the request &MAY; be automatically redirected by the user agent without
confirmation. Otherwise, the user agent &MUST-NOT; automatically redirect the
request unless it can be confirmed by the user, since this might
change the conditions under which the request was issued.
Note: For historic reasons, user agents &MAY; change the
request method from POST to GET for the subsequent request. If this
behavior is undesired, status code 307 (Temporary Redirect) can be used
instead.
but see
The 303 status code indicates that the server is redirecting the
user agent to a different resource, as indicated by a URI in the
Location header field, that is intended to provide an indirect
response to the original request. In order to satisfy the original
request, a user agent &SHOULD; perform a retrieval request using the
Location URI (a GET or HEAD request if using HTTP), which
may itself be redirected further, and present the eventual result as an
answer to the original request.
Note that the new URI in the Location header field is not considered
equivalent to the effective request URI.
This status code is generally applicable to any HTTP method. It is
primarily used to allow the output of a POST action to redirect
the user agent to a selected resource, since doing so provides the
information corresponding to the POST response in a form that
can be separately identified, bookmarked, and cached independent
of the original request.
A 303 response to a GET request indicates that the requested
resource does not have a representation of its own that can be
transferred by the server over HTTP. The Location URI indicates a
resource that is descriptive of the target resource, such that the
follow-on representation might be useful to recipients without
implying that it adequately represents the target resource.
Note that answers to the questions of what can be represented, what
representations are adequate, and what might be a useful description
are outside the scope of HTTP and thus entirely determined by the
URI owner(s).
Except for responses to a HEAD request, the representation of a 303
response &SHOULD; contain a short hypertext note with a hyperlink
to the Location URI.
Part4
The response to the request has not been modified since the conditions
indicated by the client's conditional GET request, as defined in &status-304;.
The 305 status code was defined in a previous version of this specification
(see ), and is now deprecated.
The 306 status code was used in a previous version of the
specification, is no longer used, and the code is reserved.
The target resource resides temporarily under a different URI.
Since the redirection can change over time, the client &SHOULD;
continue to use the effective request URI for future requests.
The temporary URI &SHOULD; be given by the Location field in the
response. Unless the request method was HEAD, the representation of the
response &SHOULD; contain a short hypertext note with a hyperlink to
the new URI(s), since many pre-HTTP/1.1 user agents do not
understand the 307 status code. Therefore, the note &SHOULD; contain the
information necessary for a user to repeat the original request on
the new URI.
If the 307 status code is received in response to a request method
that is known to be "safe", as defined in ,
then the request &MAY; be automatically redirected by the user agent without
confirmation. Otherwise, the user agent &MUST-NOT; automatically redirect the
request unless it can be confirmed by the user, since this might
change the conditions under which the request was issued.
Note: This status code is similar to 302 Found, except that
it does not allow rewriting the request method from POST to GET. This
specification defines no equivalent counterpart for 301 Moved Permanently.
The 4xx class of status code is intended for cases in which the
client seems to have erred. Except when responding to a HEAD request,
the server &SHOULD; include a representation containing an explanation of the
error situation, and whether it is a temporary or permanent
condition. These status codes are applicable to any request method.
User agents &SHOULD; display any included representation to the user.
If the client is sending data, a server implementation using TCP
&SHOULD; be careful to ensure that the client acknowledges receipt of
the packet(s) containing the response, before the server closes the
input connection. If the client continues sending data to the server
after the close, the server's TCP stack will send a reset packet to
the client, which might erase the client's unacknowledged input buffers
before they can be read and interpreted by the HTTP application.
The server cannot or will not process the request, due to a client error (e.g.,
malformed syntax).Part7
The request requires user authentication (see &status-401;).
This code is reserved for future use.
The server understood the request, but refuses to authorize it. Providing
different user authentication credentials might be successful, but any
credentials that were provided in the request are insufficient. The request
&SHOULD-NOT; be repeated with the same credentials.
If the request method was not HEAD and the server wishes to make
public why the request has not been fulfilled, it &SHOULD; describe the
reason for the refusal in the representation. If the server does not wish to
make this information available to the client, the status code 404
(Not Found) &MAY; be used instead.
The server has not found anything matching the effective request URI. No
indication is given of whether the condition is temporary or
permanent. The 410 (Gone) status code &SHOULD; be used if the server
knows, through some internally configurable mechanism, that an old
resource is permanently unavailable and has no forwarding address.
This status code is commonly used when the server does not wish to
reveal exactly why the request has been refused, or when no other
response is applicable.
The method specified in the Request-Line is not allowed for the target
resource. The response &MUST; include an Allow header field containing a
list of valid methods for the requested resource.
The resource identified by the request is only capable of generating
response representations which have content characteristics not acceptable
according to the Accept and Accept-* header fields sent in the request
(see &p3-header-fields;).
Unless it was a HEAD request, the response &SHOULD; include a representation
containing a list of available representation characteristics and location(s)
from which the user or user agent can choose the one most
appropriate. The data format is specified by the media type given
in the Content-Type header field. Depending upon the format and the
capabilities of the user agent, selection of the most appropriate
choice &MAY; be performed automatically. However, this specification
does not define any standard for such automatic selection.
Note: HTTP/1.1 servers are allowed to return responses which are
not acceptable according to the accept header fields sent in the
request. In some cases, this might even be preferable to sending a
406 response. User agents are encouraged to inspect the header fields of
an incoming response to determine if it is acceptable.
If the response could be unacceptable, a user agent &SHOULD;
temporarily stop receipt of more data and query the user for a
decision on further actions.
This code is similar to 401 (Unauthorized), but indicates that the
client must first authenticate itself with the proxy (see &status-407;).
The client did not produce a request within the time that the server
was prepared to wait. The client &MAY; repeat the request without
modifications at any later time.
The request could not be completed due to a conflict with the current
state of the resource. This code is only allowed in situations where
it is expected that the user might be able to resolve the conflict
and resubmit the request. The response body &SHOULD; include enough
information for the user to recognize the source of the conflict.
Ideally, the response representation would include enough information for the
user or user agent to fix the problem; however, that might not be
possible and is not required.
Conflicts are most likely to occur in response to a PUT request. For
example, if versioning were being used and the representation being PUT
included changes to a resource which conflict with those made by an
earlier (third-party) request, the server might use the 409 response
to indicate that it can't complete the request. In this case, the
response representation would likely contain a list of the differences
between the two versions in a format defined by the response
Content-Type.
The target resource is no longer available at the server and no
forwarding address is known. This condition is expected to be
considered permanent. Clients with link editing capabilities &SHOULD;
delete references to the effective request URI after user approval. If the
server does not know, or has no facility to determine, whether or not
the condition is permanent, the status code 404 (Not Found) &SHOULD; be
used instead.
The 410 response is primarily intended to assist the task of web
maintenance by notifying the recipient that the resource is
intentionally unavailable and that the server owners desire that
remote links to that resource be removed. Such an event is common for
limited-time, promotional services and for resources belonging to
individuals no longer working at the server's site. It is not
necessary to mark all permanently unavailable resources as "gone" or
to keep the mark for any length of time — that is left to the
discretion of the server owner.
Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
for 410 responses.
The server refuses to accept the request without a defined Content-Length.
The client &MAY; repeat the request if it adds a valid
Content-Length header field containing the length of the message-body
in the request message.
Part4
The precondition given in one or more of the header fields
evaluated to false when it was tested on the server, as defined in
&status-412;.
The server is refusing to process a request because the request
representation is larger than the server is willing or able to process. The
server &MAY; close the connection to prevent the client from continuing
the request.
If the condition is temporary, the server &SHOULD; include a Retry-After
header field to indicate that it is temporary and after what
time the client &MAY; try again.
The server is refusing to service the request because the effective request URI
is longer than the server is willing to interpret. This rare
condition is only likely to occur when a client has improperly
converted a POST request to a GET request with long query
information, when the client has descended into a URI "black hole" of
redirection (e.g., a redirected URI prefix that points to a suffix of
itself), or when the server is under attack by a client attempting to
exploit security holes present in some servers using fixed-length
buffers for reading or manipulating the effective request URI.
The server is refusing to service the request because the request
payload is in a format not supported by this request method on the
target resource.
Part5
The request included a Range header field (&header-range;) and none of
the range-specifier values in this field overlap the current extent
of the selected resource. See &status-416;.
The expectation given in an Expect header field (see )
could not be met by this server, or, if the server is a proxy,
the server has unambiguous evidence that the request could not be met
by the next-hop server.
The request can not be completed without a prior protocol upgrade. This
response &MUST; include an Upgrade header field (&header-upgrade;)
specifying the required protocols.
Example:
HTTP/1.1 426 Upgrade Required
Upgrade: HTTP/2.0
Connection: Upgrade
The server &SHOULD; include a message body in the 426 response which
indicates in human readable form the reason for the error and describes any
alternative courses which may be available to the user.
Response status codes beginning with the digit "5" indicate cases in
which the server is aware that it has erred or is incapable of
performing the request. Except when responding to a HEAD request, the
server &SHOULD; include a representation containing an explanation of the
error situation, and whether it is a temporary or permanent
condition. User agents &SHOULD; display any included representation to the
user. These response codes are applicable to any request method.
The server encountered an unexpected condition which prevented it
from fulfilling the request.
The server does not support the functionality required to fulfill the
request. This is the appropriate response when the server does not
recognize the request method and is not capable of supporting it for
any resource.
The server, while acting as a gateway or proxy, received an invalid
response from the upstream server it accessed in attempting to
fulfill the request.
The server is currently unable to handle the request due to a
temporary overloading or maintenance of the server.
The implication is that this is a temporary condition which will be
alleviated after some delay. If known, the length of the delay &MAY; be
indicated in a Retry-After header field ().
If no Retry-After is given, the client &SHOULD; handle the response as it
would for a 500 response.
Note: The existence of the 503 status code does not imply that a
server must use it when becoming overloaded. Some servers might wish
to simply refuse the connection.
The server, while acting as a gateway or proxy, did not receive a
timely response from the upstream server specified by the URI (e.g.,
HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
to access in attempting to complete the request.
Note to implementors: some deployed proxies are known to
return 400 or 500 when DNS lookups time out.
The server does not support, or refuses to support, the protocol
version that was used in the request message. The server is
indicating that it is unable or unwilling to complete the request
using the same major version as the client, as described in &http-version;,
other than with this error message. The response &SHOULD; contain
a representation describing why that version is not supported and what other
protocols are supported by that server.
HTTP applications have historically allowed three different formats
for date/time stamps. However, the preferred format is a fixed-length subset
of that defined by :
Sun, 06 Nov 1994 08:49:37 GMT ; RFC 1123
The other formats are described here only for compatibility with obsolete
implementations.
Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
Sun Nov 6 08:49:37 1994 ; ANSI C's asctime() format
HTTP/1.1 clients and servers that parse a date value &MUST; accept
all three formats (for compatibility with HTTP/1.0), though they &MUST;
only generate the RFC 1123 format for representing HTTP-date values
in header fields.
All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
(GMT), without exception. For the purposes of HTTP, GMT is exactly
equal to UTC (Coordinated Universal Time). This is indicated in the
first two formats by the inclusion of "GMT" as the three-letter
abbreviation for time zone, and &MUST; be assumed when reading the
asctime format. HTTP-date is case sensitive and &MUST-NOT; include
additional whitespace beyond that specifically included as SP in the
grammar.
HTTP-date = rfc1123-date / obs-date
Preferred format:
rfc1123-date = day-name "," SP date1 SPtime-of-daySPGMT
; fixed length subset of the format defined in
; day-name = "Mon" ; "Mon", case-sensitive
/ "Tue" ; "Tue", case-sensitive
/ "Wed" ; "Wed", case-sensitive
/ "Thu" ; "Thu", case-sensitive
/ "Fri" ; "Fri", case-sensitive
/ "Sat" ; "Sat", case-sensitive
/ "Sun" ; "Sun", case-sensitive
date1 = daySPmonthSPyear
; e.g., 02 Jun 1982
day = 2DIGITmonth = "Jan" ; "Jan", case-sensitive
/ "Feb" ; "Feb", case-sensitive
/ "Mar" ; "Mar", case-sensitive
/ "Apr" ; "Apr", case-sensitive
/ "May" ; "May", case-sensitive
/ "Jun" ; "Jun", case-sensitive
/ "Jul" ; "Jul", case-sensitive
/ "Aug" ; "Aug", case-sensitive
/ "Sep" ; "Sep", case-sensitive
/ "Oct" ; "Oct", case-sensitive
/ "Nov" ; "Nov", case-sensitive
/ "Dec" ; "Dec", case-sensitive
year = 4DIGITGMT = "GMT" ; "GMT", case-sensitive
time-of-day = hour ":" minute ":" second
; 00:00:00 - 23:59:59
hour = 2DIGITminute = 2DIGITsecond = 2DIGIT
The semantics of day-name, day,
month, year, and time-of-day are the
same as those defined for the RFC 5322 constructs
with the corresponding name ().
Obsolete formats:
obs-date = rfc850-date / asctime-daterfc850-date = day-name-l "," SPdate2SPtime-of-daySPGMTdate2 = day "-" month "-" 2DIGIT
; day-month-year (e.g., 02-Jun-82)
day-name-l = "Monday" ; "Monday", case-sensitive
/ "Tuesday" ; "Tuesday", case-sensitive
/ "Wednesday" ; "Wednesday", case-sensitive
/ "Thursday" ; "Thursday", case-sensitive
/ "Friday" ; "Friday", case-sensitive
/ "Saturday" ; "Saturday", case-sensitive
/ "Sunday" ; "Sunday", case-sensitive
asctime-date = day-nameSPdate3SPtime-of-daySPyeardate3 = monthSP ( 2DIGIT / ( SP 1DIGIT ))
; month day (e.g., Jun 2)
Note: Recipients of date values are encouraged to be robust in
accepting date values that might have been sent by non-HTTP
applications, as is sometimes the case when retrieving or posting
messages via proxies/gateways to SMTP or NNTP.
Note: HTTP requirements for the date/time stamp format apply only
to their usage within the protocol stream. Clients and servers are
not required to use these formats for user presentation, request
logging, etc.
This section defines the syntax and semantics of HTTP/1.1 header fields
related to request and response semantics.
The "Allow" header field lists the set of methods advertised as
supported by the target resource. The purpose of this field is strictly to
inform the recipient of valid request methods associated with the resource.
Allow = #Method
Example of use:
Allow: GET, HEAD, PUT
The actual set of allowed methods is defined by the origin server at the
time of each request.
A proxy &MUST-NOT; modify the Allow header field — it does not need to
understand all the methods specified in order to handle them according to
the generic message handling rules.
The "Date" header field represents the date and time at which
the message was originated, having the same semantics as the Origination
Date Field (orig-date) defined in .
The field value is an HTTP-date, as defined in ;
it &MUST; be sent in rfc1123-date format.
Date = HTTP-date
An example is
Date: Tue, 15 Nov 1994 08:12:31 GMT
Origin servers &MUST; include a Date header field in all responses,
except in these cases:
If the response status code is 100 (Continue) or 101 (Switching
Protocols), the response &MAY; include a Date header field, at
the server's option.If the response status code conveys a server error, e.g., 500
(Internal Server Error) or 503 (Service Unavailable), and it is
inconvenient or impossible to generate a valid Date.If the server does not have a clock that can provide a
reasonable approximation of the current time, its responses
&MUST-NOT; include a Date header field.
A received message that does not have a Date header field &MUST; be
assigned one by the recipient if the message will be cached by that
recipient.
Clients can use the Date header field as well; in order to keep request
messages small, they are advised not to include it when it doesn't convey
any useful information (as it is usually the case for requests that do not
contain a payload).
The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
time subsequent to the generation of the message. It &SHOULD; represent
the best available approximation of the date and time of message
generation, unless the implementation has no means of generating a
reasonably accurate date and time. In theory, the date ought to
represent the moment just before the payload is generated. In
practice, the date can be generated at any time during the message
origination without affecting its semantic value.
The "Expect" header field is used to indicate that particular
server behaviors are required by the client.
Expect = 1#expectationexpectation = expect-name [ BWS "=" BWSexpect-value ]
*( OWS ";" [ OWSexpect-param ] )
expect-param = expect-name [ BWS "=" BWSexpect-value ]
expect-name = tokenexpect-value = token / quoted-string
If all received Expect header field(s) are syntactically valid but contain
an expectation that the recipient does not understand or cannot comply with,
the recipient &MUST; respond with a 417 (Expectation Failed) status code. A
recipient of a syntactically invalid Expectation header field &MUST; respond
with a 4xx status code other than 417.
The only expectation defined by this specification is:
100-continue
The "100-continue" expectation is defined &use100;. It does not support
any expect-params.
Comparison is case-insensitive for names (expect-name), and case-sensitive
for values (expect-value).
The Expect mechanism is hop-by-hop: the above requirements apply to any
server, including proxies. However, the Expect header field itself is
end-to-end; it &MUST; be forwarded if the request is forwarded.
Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect
header field.
The "From" header field, if given, &SHOULD; contain an Internet
e-mail address for the human user who controls the requesting user
agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
in :
From = mailboxmailbox = <mailbox, defined in >
An example is:
From: webmaster@example.org
This header field &MAY; be used for logging purposes and as a means for
identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
be used as an insecure form of access protection. The interpretation
of this field is that the request is being performed on behalf of the
person given, who accepts responsibility for the method performed. In
particular, robot agents &SHOULD; include this header field so that the
person responsible for running the robot can be contacted if problems
occur on the receiving end.
The Internet e-mail address in this field &MAY; be separate from the
Internet host which issued the request. For example, when a request
is passed through a proxy the original issuer's address &SHOULD; be
used.
The client &SHOULD-NOT; send the From header field without the user's
approval, as it might conflict with the user's privacy interests or
their site's security policy. It is strongly recommended that the
user be able to disable, enable, and modify the value of this field
at any time prior to a request.
The "Location" header field is used to identify a newly created
resource, or to redirect the recipient to a different location for
completion of the request.
For 201 (Created) responses, the Location is the URI of the new resource
which was created by the request. For 3xx responses, the location &SHOULD;
indicate the server's preferred URI for automatic redirection to the
resource.
The field value consists of a single URI-reference. When it has the form
of a relative reference (),
the final value is computed by resolving it against the effective request
URI ().
Location = URI-referenceExamples are:
Location: http://www.example.org/pub/WWW/People.html#tim
Location: /index.html
Note: Some recipients attempt to recover from Location fields
that are not valid URI references. This specification does not mandate or
define such processing, but does allow it (see ).
There are circumstances in which a fragment identifier in a Location URI
would not be appropriate. For instance, when it appears in a 201 Created
response, where the Location header field specifies the URI for the entire
created resource.
Note: This specification does not define precedence rules
for the case where the original URI, as navigated to by the user
agent, and the Location header field value both contain fragment
identifiers. Thus be aware that including fragment identifiers might
inconvenience anyone relying on the semantics of the original URI's
fragment identifier.
Note: The Content-Location header field (&header-content-location;) differs
from Location in that the Content-Location identifies the most specific
resource corresponding to the enclosed representation.
It is therefore possible for a response to contain header fields for
both Location and Content-Location.
The "Max-Forwards" header field provides a mechanism with the
TRACE () and OPTIONS ()
methods to limit the number of times that the request is forwarded by
proxies. This can be useful when the client is attempting to
trace a request which appears to be failing or looping in mid-chain.
Max-Forwards = 1*DIGIT
The Max-Forwards value is a decimal integer indicating the remaining
number of times this request message can be forwarded.
Each recipient of a TRACE or OPTIONS request
containing a Max-Forwards header field &MUST; check and update its
value prior to forwarding the request. If the received value is zero
(0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
respond as the final recipient. If the received Max-Forwards value is
greater than zero, then the forwarded message &MUST; contain an updated
Max-Forwards field with a value decremented by one (1).
The Max-Forwards header field &MAY; be ignored for all other request
methods.
The "Referer" [sic] header field allows the client to specify the
URI of the resource from which the effective request URI was obtained (the
"referrer", although the header field is misspelled.).
The Referer header field allows servers to generate lists of back-links to
resources for interest, logging, optimized caching, etc. It also allows
obsolete or mistyped links to be traced for maintenance. Some servers use
Referer as a means of controlling where they allow links from (so-called
"deep linking"), but legitimate requests do not always
contain a Referer header field.
If the effective request URI was obtained from a source that does not have its own
URI (e.g., input from the user keyboard), the Referer field &MUST; either be
sent with the value "about:blank", or not be sent at all. Note that this
requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
Referer = absolute-URI / partial-URI
Example:
Referer: http://www.example.org/hypertext/Overview.html
If the field value is a relative URI, it &SHOULD; be interpreted
relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
for security considerations.
The header "Retry-After" field can be used with a 503 (Service
Unavailable) response to indicate how long the service is expected to
be unavailable to the requesting client. This field &MAY; also be used
with any 3xx (Redirection) response to indicate the minimum time the
user-agent is asked wait before issuing the redirected request.
The value of this field can be either an HTTP-date or an integer number
of seconds (in decimal) after the time of the response.
Retry-After = HTTP-date / delta-seconds
Time spans are non-negative decimal integers, representing time in
seconds.
delta-seconds = 1*DIGIT
Two examples of its use are
Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
Retry-After: 120
In the latter example, the delay is 2 minutes.
The "Server" header field contains information about the
software used by the origin server to handle the request.
The field can contain multiple product tokens (&product-tokens;) and
comments (&header-fields;) identifying the server and any significant
subproducts. The product tokens are listed in order of their significance
for identifying the application.
Server = product *( RWS ( product / comment ) )
Example:
Server: CERN/3.0 libwww/2.17
If the response is being forwarded through a proxy, the proxy
application &MUST-NOT; modify the Server header field. Instead, it
&MUST; include a Via field (as described in &header-via;).
Note: Revealing the specific software version of the server might
allow the server machine to become more vulnerable to attacks
against software that is known to contain security holes. Server
implementors are encouraged to make this field a configurable
option.
The "User-Agent" header field contains information about the user
agent originating the request. User agents &SHOULD; include this field with
requests.
Typically, it is used for statistical purposes, the tracing of protocol
violations, and tailoring responses to avoid particular user agent
limitations.
The field can contain multiple product tokens (&product-tokens;)
and comments (&header-fields;) identifying the agent and its
significant subproducts. By convention, the product tokens are listed in
order of their significance for identifying the application.
Because this field is usually sent on every request a user agent makes,
implementations are encouraged not to include needlessly fine-grained
detail, and to limit (or even prohibit) the addition of subproducts by third
parties. Overly long and detailed User-Agent field values make requests
larger and can also be used to identify ("fingerprint") the user against
their wishes.
Likewise, implementations are encouraged not to use the product tokens of
other implementations in order to declare compatibility with them, as this
circumvents the purpose of the field. Finally, they are encouraged not to
use comments to identify products; doing so makes the field value more
difficult to parse.
User-Agent = product *( RWS ( product / comment ) )
Example:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3
The registration procedure for HTTP request methods is defined by
of this document.
The HTTP Method Registry shall be created at
and be populated with the registrations below:
MethodSafeReferenceCONNECTnoDELETEnoGETyesHEADyesOPTIONSyesPOSTnoPUTnoTRACEyes
The registration procedure for HTTP Status Codes — previously defined
in — is now defined
by of this document.
The HTTP Status Code Registry located at
shall be updated with the registrations below:
ValueDescriptionReference100Continue101Switching Protocols200OK201Created202Accepted203Non-Authoritative Information204No Content205Reset Content300Multiple Choices301Moved Permanently302Found303See Other305Use Proxy306(Unused)307Temporary Redirect400Bad Request402Payment Required403Forbidden404Not Found405Method Not Allowed406Not Acceptable407Proxy Authentication Required408Request Timeout409Conflict410Gone411Length Required413Request Representation Too Large414URI Too Long415Unsupported Media Type417Expectation Failed426Upgrade Required500Internal Server Error501Not Implemented502Bad Gateway503Service Unavailable504Gateway Timeout505HTTP Version Not Supported
The Message Header Field Registry located at shall be updated
with the permanent registrations below (see ):
Header Field NameProtocolStatusReferenceAllowhttpstandardDatehttpstandardExpecthttpstandardFromhttpstandardLocationhttpstandardMax-ForwardshttpstandardRefererhttpstandardRetry-AfterhttpstandardServerhttpstandardUser-Agenthttpstandard
The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
This section is meant to inform application developers, information
providers, and users of the security limitations in HTTP/1.1 as
described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make
some suggestions for reducing security risks.
Like any generic data transfer protocol, HTTP cannot regulate the
content of the data that is transferred, nor is there any a priori
method of determining the sensitivity of any particular piece of
information within the context of any given request. Therefore,
applications &SHOULD; supply as much control over this information as
possible to the provider of that information. Four header fields are
worth special mention in this context: Server, Via, Referer and From.
Revealing the specific software version of the server might allow the
server machine to become more vulnerable to attacks against software
that is known to contain security holes. Implementors &SHOULD; make the
Server header field a configurable option.
Proxies which serve as a portal through a network firewall &SHOULD;
take special precautions regarding the transfer of header information
that identifies the hosts behind the firewall. In particular, they
&SHOULD; remove, or replace with sanitized versions, any Via fields
generated behind the firewall.
The Referer header field allows reading patterns to be studied and reverse
links drawn. Although it can be very useful, its power can be abused
if user details are not separated from the information contained in
the Referer. Even when the personal information has been removed, the
Referer header field might indicate a private document's URI whose
publication would be inappropriate.
The information sent in the From field might conflict with the user's
privacy interests or their site's security policy, and hence it
&SHOULD-NOT; be transmitted without the user being able to disable,
enable, and modify the contents of the field. The user &MUST; be able
to set the contents of this field within a user preference or
application defaults configuration.
We suggest, though do not require, that a convenient toggle interface
be provided for the user to enable or disable the sending of From and
Referer information.
The User-Agent () or Server () header fields can sometimes be used to determine
that a specific client or server have a particular security hole which might
be exploited. Unfortunately, this same information is often used for other
valuable purposes for which HTTP currently has no better mechanism.
Furthermore, the User-Agent header field may contain enough entropy to be
used, possibly in conjunction with other material, to uniquely identify the
user.
Some request methods, like TRACE (), expose information
that was sent in request header fields within the body of their response.
Clients &SHOULD; be careful with sensitive information, like Cookies,
Authorization credentials, and other header fields that might be used to
collect data from the client.
Because the source of a link might be private information or might
reveal an otherwise private information source, it is strongly
recommended that the user be able to select whether or not the
Referer field is sent. For example, a browser client could have a
toggle switch for browsing openly/anonymously, which would
respectively enable/disable the sending of Referer and From
information.
Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
HTTP request if the referring page was transferred with a secure
protocol.
Authors of services &SHOULD-NOT; use GET-based forms for the submission of
sensitive data because that data will be placed in the request-target. Many
existing servers, proxies, and user agents log or display the request-target
in places where it might be visible to third parties. Such services can
use POST-based form submission instead.
If a single server supports multiple organizations that do not trust
one another, then it &MUST; check the values of Location and Content-Location
header fields in responses that are generated under control of
said organizations to make sure that they do not attempt to
invalidate resources over which they have no authority.
Since tunneled data is opaque to the proxy, there are additional
risks to tunneling to other well-known or reserved ports.
A HTTP client CONNECTing to port 25 could relay spam
via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
access to a small number of known ports.
See &acks;.
HTTP/1.1, part 1: URIs, Connections, and Message ParsingAdobe Systems Incorporatedfielding@gbiv.comAlcatel-Lucent Bell Labsjg@freedesktop.orgHewlett-Packard CompanyJeffMogul@acm.orgMicrosoft Corporationhenrikn@microsoft.comAdobe Systems IncorporatedLMM@acm.orgMicrosoft Corporationpaulle@microsoft.comWorld Wide Web Consortiumtimbl@w3.orgWorld Wide Web Consortiumylafon@w3.orggreenbytes GmbHjulian.reschke@greenbytes.deHTTP/1.1, part 3: Message Payload and Content NegotiationAdobe Systems Incorporatedfielding@gbiv.comAlcatel-Lucent Bell Labsjg@freedesktop.orgHewlett-Packard CompanyJeffMogul@acm.orgMicrosoft Corporationhenrikn@microsoft.comAdobe Systems IncorporatedLMM@acm.orgMicrosoft Corporationpaulle@microsoft.comWorld Wide Web Consortiumtimbl@w3.orgWorld Wide Web Consortiumylafon@w3.orggreenbytes GmbHjulian.reschke@greenbytes.deHTTP/1.1, part 4: Conditional RequestsAdobe Systems Incorporatedfielding@gbiv.comAlcatel-Lucent Bell Labsjg@freedesktop.orgHewlett-Packard CompanyJeffMogul@acm.orgMicrosoft Corporationhenrikn@microsoft.comAdobe Systems IncorporatedLMM@acm.orgMicrosoft Corporationpaulle@microsoft.comWorld Wide Web Consortiumtimbl@w3.orgWorld Wide Web Consortiumylafon@w3.orggreenbytes GmbHjulian.reschke@greenbytes.deHTTP/1.1, part 5: Range Requests and Partial ResponsesAdobe Systems Incorporatedfielding@gbiv.comAlcatel-Lucent Bell Labsjg@freedesktop.orgHewlett-Packard CompanyJeffMogul@acm.orgMicrosoft Corporationhenrikn@microsoft.comAdobe Systems IncorporatedLMM@acm.orgMicrosoft Corporationpaulle@microsoft.comWorld Wide Web Consortiumtimbl@w3.orgWorld Wide Web Consortiumylafon@w3.orggreenbytes GmbHjulian.reschke@greenbytes.deHTTP/1.1, part 6: CachingAdobe Systems Incorporatedfielding@gbiv.comAlcatel-Lucent Bell Labsjg@freedesktop.orgHewlett-Packard CompanyJeffMogul@acm.orgMicrosoft Corporationhenrikn@microsoft.comAdobe Systems IncorporatedLMM@acm.orgMicrosoft Corporationpaulle@microsoft.comWorld Wide Web Consortiumtimbl@w3.orgWorld Wide Web Consortiumylafon@w3.orgRackspacemnot@mnot.netgreenbytes GmbHjulian.reschke@greenbytes.deHTTP/1.1, part 7: AuthenticationAdobe Systems Incorporatedfielding@gbiv.comAlcatel-Lucent Bell Labsjg@freedesktop.orgHewlett-Packard CompanyJeffMogul@acm.orgMicrosoft Corporationhenrikn@microsoft.comAdobe Systems IncorporatedLMM@acm.orgMicrosoft Corporationpaulle@microsoft.comWorld Wide Web Consortiumtimbl@w3.orgWorld Wide Web Consortiumylafon@w3.orggreenbytes GmbHjulian.reschke@greenbytes.deKey words for use in RFCs to Indicate Requirement LevelsHarvard Universitysob@harvard.eduUniform Resource Identifier (URI): Generic SyntaxWorld Wide Web Consortiumtimbl@w3.orghttp://www.w3.org/People/Berners-Lee/Day Softwarefielding@gbiv.comhttp://roy.gbiv.com/Adobe Systems IncorporatedLMM@acm.orghttp://larry.masinter.net/Augmented BNF for Syntax Specifications: ABNFBrandenburg InternetWorkingdcrocker@bbiw.netTHUS plc.paul.overell@thus.netRequirements for Internet Hosts - Application and SupportUniversity of Southern California (USC), Information Sciences InstituteBraden@ISI.EDUHypertext Transfer Protocol -- HTTP/1.0MIT, Laboratory for Computer Sciencetimbl@w3.orgUniversity of California, Irvine, Department of Information and Computer Sciencefielding@ics.uci.eduW3 Consortium, MIT Laboratory for Computer Sciencefrystyk@w3.orgHypertext Transfer Protocol -- HTTP/1.1University of California, Irvine, Department of Information and Computer Sciencefielding@ics.uci.eduMIT Laboratory for Computer Sciencejg@w3.orgDigital Equipment Corporation, Western Research Laboratorymogul@wrl.dec.comMIT Laboratory for Computer Sciencefrystyk@w3.orgMIT Laboratory for Computer Sciencetimbl@w3.orgHypertext Transfer Protocol -- HTTP/1.1University of California, Irvinefielding@ics.uci.eduW3Cjg@w3.orgCompaq Computer Corporationmogul@wrl.dec.comMIT Laboratory for Computer Sciencefrystyk@w3.orgXerox Corporationmasinter@parc.xerox.comMicrosoft Corporationpaulle@microsoft.comW3Ctimbl@w3.orgUpgrading to TLS Within HTTP/1.14K Associates / UC Irvinerohit@4K-associates.comAgranat Systems, Inc.lawrence@agranat.comRegistration Procedures for Message Header FieldsNine by NineGK-IETF@ninebynine.orgBEA Systemsmnot@pobox.comHP LabsJeffMogul@acm.orgGuidelines for Writing an IANA Considerations Section in RFCsIBMnarten@us.ibm.comGoogleHarald@Alvestrand.noInternet Message FormatQualcomm IncorporatedPATCH Method for HTTPLinden LabCharacter Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parametersgreenbytes GmbHHafenweg 16MuensterNW48155Germanyjulian.reschke@greenbytes.dehttp://greenbytes.de/tech/webdav/
This document takes over the Status Code Registry, previously defined
in .
()
Clarify definition of POST.
()
Remove requirement to handle all Content-* header fields; ban use of
Content-Range with PUT.
()
Take over definition of CONNECT method from .
()
Broadened the definition of 203 (Non-Authoritative Information) to include
cases of payload transformations as well.
()
Failed to consider that there are many other request methods that are safe
to automatically redirect, and further that the user agent is able to make
that determination based on the request method semantics.
Furthermore, allow user agents to rewrite the method from POST to GET
for status codes 301 and 302.
(Sections ,
and
)
Deprecate 305 Use Proxy status code, because user agents did not implement it.
It used to indicate that the target resource must be accessed through the
proxy given by the Location field. The Location field gave the URI of the
proxy. The recipient was expected to repeat this single request via the proxy.
()
Define status 426 (Upgrade Required) (this was incorporated from
).
()
Change ABNF productions for header fields to only define the field value.
()
Reclassify "Allow" as response header field, removing the option to
specify it in a PUT request.
Relax the server requirement on the contents of the Allow header field and
remove requirement on clients to always trust the header field value.
()
The ABNF for the Expect header field has been both fixed (allowing parameters
for value-less expectations as well) and simplified (allowing trailing
semicolons after "100-continue" when they were invalid before).
()
Correct syntax of Location header field to allow URI references (including
relative references and fragments), as referred symbol "absoluteURI" wasn't
what was expected, and add some clarifications as to when use of fragments
would not be appropriate.
()
Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
extension methods could have used it as well).
()
Allow Referer field value of "about:blank" as alternative to not specifying it.
()
In the description of the Server header field, the Via field
was described as a SHOULD. The requirement was and is stated
correctly in the description of the Via header field in &header-via;.
()
Allow = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
BWS = <BWS, defined in [Part1], Section 1.2.2>
Date = HTTP-date
Expect = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
From = mailbox
GMT = %x47.4D.54 ; GMT
HTTP-date = rfc1123-date / obs-date
Location = URI-reference
Max-Forwards = 1*DIGIT
Method = token
OWS = <OWS, defined in [Part1], Section 1.2.2>
RWS = <RWS, defined in [Part1], Section 1.2.2>
Reason-Phrase = *( HTAB / SP / VCHAR / obs-text )
Referer = absolute-URI / partial-URI
Retry-After = HTTP-date / delta-seconds
Server = product *( RWS ( product / comment ) )
Status-Code = 3DIGIT
URI-reference = <URI-reference, defined in [Part1], Section 2.7>
User-Agent = product *( RWS ( product / comment ) )
absolute-URI = <absolute-URI, defined in [Part1], Section 2.7>
asctime-date = day-name SP date3 SP time-of-day SP year
comment = <comment, defined in [Part1], Section 3.2>
date1 = day SP month SP year
date2 = day "-" month "-" 2DIGIT
date3 = month SP ( 2DIGIT / ( SP DIGIT ) )
day = 2DIGIT
day-name = %x4D.6F.6E ; Mon
/ %x54.75.65 ; Tue
/ %x57.65.64 ; Wed
/ %x54.68.75 ; Thu
/ %x46.72.69 ; Fri
/ %x53.61.74 ; Sat
/ %x53.75.6E ; Sun
day-name-l = %x4D.6F.6E.64.61.79 ; Monday
/ %x54.75.65.73.64.61.79 ; Tuesday
/ %x57.65.64.6E.65.73.64.61.79 ; Wednesday
/ %x54.68.75.72.73.64.61.79 ; Thursday
/ %x46.72.69.64.61.79 ; Friday
/ %x53.61.74.75.72.64.61.79 ; Saturday
/ %x53.75.6E.64.61.79 ; Sunday
delta-seconds = 1*DIGIT
expect-name = token
expect-param = expect-name [ BWS "=" BWS expect-value ]
expect-value = token / quoted-string
expectation = expect-name [ BWS "=" BWS expect-value ] *( OWS ";" [
OWS expect-param ] )
hour = 2DIGIT
mailbox = <mailbox, defined in [RFC5322], Section 3.4>
minute = 2DIGIT
month = %x4A.61.6E ; Jan
/ %x46.65.62 ; Feb
/ %x4D.61.72 ; Mar
/ %x41.70.72 ; Apr
/ %x4D.61.79 ; May
/ %x4A.75.6E ; Jun
/ %x4A.75.6C ; Jul
/ %x41.75.67 ; Aug
/ %x53.65.70 ; Sep
/ %x4F.63.74 ; Oct
/ %x4E.6F.76 ; Nov
/ %x44.65.63 ; Dec
obs-date = rfc850-date / asctime-date
obs-text = <obs-text, defined in [Part1], Section 1.2.2>
partial-URI = <partial-URI, defined in [Part1], Section 2.7>
product = <product, defined in [Part1], Section 5.2>
quoted-string = <quoted-string, defined in [Part1], Section 3.2.3>
rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT
rfc850-date = day-name-l "," SP date2 SP time-of-day SP GMT
second = 2DIGIT
time-of-day = hour ":" minute ":" second
token = <token, defined in [Part1], Section 3.2.3>
year = 4DIGIT
ABNF diagnostics:
; Allow defined but not used
; Date defined but not used
; Expect defined but not used
; From defined but not used
; Location defined but not used
; Max-Forwards defined but not used
; Reason-Phrase defined but not used
; Referer defined but not used
; Retry-After defined but not used
; Server defined but not used
; Status-Code defined but not used
; User-Agent defined but not used
Extracted relevant partitions from .
Closed issues:
:
"Via is a MUST"
()
:
"Fragments allowed in Location"
()
:
"Safe Methods vs Redirection"
()
:
"Revise description of the POST method"
()
:
"Normative and Informative references"
:
"RFC2606 Compliance"
:
"Informative references"
:
"Redundant cross-references"
Other changes:
Move definitions of 304 and 412 condition codes to
Closed issues:
:
"PUT side effects"
:
"Duplicate Host header requirements"
Ongoing work on ABNF conversion ():
Move "Product Tokens" section (back) into Part 1, as "token" is used
in the definition of the Upgrade header field.
Add explicit references to BNF syntax and rules imported from other parts of the specification.
Copy definition of delta-seconds from Part6 instead of referencing it.
Closed issues:
:
"Requiring Allow in 405 responses"
:
"Status Code Registry"
:
"Redirection vs. Location"
:
"Cacheability of 303 response"
:
"305 Use Proxy"
:
"Classification for Allow header"
:
"PUT - 'store under' vs 'store at'"
Ongoing work on IANA Message Header Field Registration ():
Reference RFC 3984, and update header field registrations for headers defined
in this document.
Ongoing work on ABNF conversion ():
Replace string literals when the string really is case-sensitive (method).
Closed issues:
:
"OPTIONS request bodies"
:
"Description of CONNECT should refer to RFC2817"
:
"Location Content-Location reference request/response mixup"
Ongoing work on Method Registry ():
Added initial proposal for registration process, plus initial
content (non-HTTP/1.1 methods to be added by a separate specification).
Closed issues:
:
"Content-*"
:
"RFC 2822 is updated by RFC 5322"
Ongoing work on ABNF conversion ():
Use "/" instead of "|" for alternatives.
Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
whitespace ("OWS") and required whitespace ("RWS").
Rewrite ABNFs to spell out whitespace rules, factor out
header field value format definitions.
Closed issues:
:
"Reason-Phrase BNF"
Final work on ABNF conversion ():
Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
Closed issues:
:
"Clarify when Referer is sent"
:
"status codes vs methods"
:
"Do not require "updates" relation for specs that register status codes or method names"
Closed issues:
:
"Idempotency"
:
"TRACE security considerations"
:
"Clarify rules for determining what entities a response carries"
:
"update note citing RFC 1945 and 2068"
:
"update note about redirect limit"
:
"Location header ABNF should use 'URI'"
:
"fragments in Location vs status 303"
:
"move IANA registrations for optional status codes"
Partly resolved issues:
:
"Are OPTIONS and TRACE safe?"
Closed issues:
:
"Safe Methods vs Redirection" (we missed the introduction to the 3xx
status codes when fixing this previously)
Closed issues:
:
"Fragment combination / precedence during redirects"
Partly resolved issues:
:
"Location header payload handling"
:
"Term for the requested resource's URI"
Closed issues:
:
"Clarify 'Requested Variant'"
:
"Clarify entity / representation / variant terminology"
:
"Methods and Caching"
:
"OPTIONS vs Max-Forwards"
:
"Status codes and caching"
:
"consider removing the 'changes from 2068' sections"
Closed issues:
:
"Considerations for new status codes"
:
"Considerations for new methods"
:
"User-Agent guidelines" (relating to the 'User-Agent' header field)
Closed issues:
:
"Fragment combination / precedence during redirects" (added warning
about having a fragid on the redirect may cause inconvenience in
some cases)
:
"Content-* vs. PUT"
:
"205 Bodies"
:
"Understanding Content-* on non-PUT requests"
:
"Content-*"
:
"Header type defaulting"
:
"PUT - 'store under' vs 'store at'"
:
"duplicate ABNF for Reason-Phrase"
:
"Note special status of Content-* prefix in header registration procedures"
:
"Max-Forwards vs extension methods"
:
"What is the value space of HTTP status codes?" (actually fixed in
draft-ietf-httpbis-p2-semantics-11)
:
"Header Classification"
:
"PUT side effect: invalidation or just stale?"
:
"proxies not supporting certain methods"
:
"Migrate CONNECT from RFC2817 to p2"
:
"Migrate Upgrade details from RFC2817"
:
"clarify PUT semantics'"
:
"duplicate ABNF for 'Method'"
:
"untangle ABNFs for header fields"
Closed issues:
:
"untangle ABNFs for header fields"
:
"message-body in CONNECT request"
Closed issues:
:
"Clarify status code for rate limiting"
:
"clarify 403 forbidden"
:
"Clarify 203 Non-Authoritative Information"
:
"update default reason phrase for 413"
Closed issues:
:
"Strength of requirements on Accept re: 406"
:
"400 response isn't generic"
Closed issues:
:
"Redirects and non-GET methods"
:
"Document HTTP's error-handling philosophy"
:
"Considerations for new headers"
:
"clarify 303 redirect on HEAD"
Closed issues:
:
"Location header payload handling"
:
"Clarify status code for rate limiting" (change backed out because
a new status code is being defined for this purpose)
:
"should there be a permanent variant of 307"
:
"When are Location's semantics triggered?"
:
"'expect' grammar missing OWS"
:
"header field considerations: quoted-string vs use of double quotes"